Infertility affects 10 to 15% of couples attempting to conceive. Male factor subfertility plays a role in about 50% of subfertile couples, with largely unknown etiology. An intervention with even a small absolute effect on any component of male factor infertility has tremendous implications at the population level because of the large potential attributable benefit. Two micronutrients fundamental to the process of spermatogenesis, folate and zinc, are of particular interest as they offer a potential low cost and widely available treatment. Though the evidence has been inconsistent, small randomized trials and observational studies show that folate and zinc have biologically plausible effects on spermatogenesis and improved semen parameters. These results support the potential benefits of folate on spermatogenesis, and suggest that supplementation with folate and zinc may improve semen quality, and perhaps, assisted reproductive technology (ART) outcomes. This is a multi-center, double-blind, randomized placebo-controlled trial to assess the effects of folic acid and zinc dietary supplementation on semen quality , and indirectly on conception rates and pregnancy outcomes among 2400 male partners of couples seeking assisted reproduction. A total of 2,400 male participants will be randomized equally (1:1) either to active study dietary supplements (folic acid and zinc daily) or to matching placebo. Only the males will be randomized to study dietary supplement or placebo. Treatment will continue for 6 months. Following a screening visit, participants will return at baseline, 2, 4, and 6 months. The trial completed recruitment in December 2017, with follow-up continuing through 2018.